Electrical stimulation of pigsÐeect on pH fall, meat quality and Cathepsin B+L activity Hanne Maribo a, *, Per Ertbjerg b , Marchen Andersson c , Patricia Barton-Gade c , Anders Juel Mùller b a DANSKE SLAGTERIER, Primary Production, Axelborg, Axeltorv 3, DK-1609 Copenhagen, Denmark b Royal Veterinary and Agricultural University, Department of Dairy and Meat Science, Rolighedsvej 30 DK 1958, Frederiksberg C, Denmark c Danish Meat Research Institute, Maglegaardsvej 2, DK-4000 Roskilde, Denmark Received 3 April 1998; received in revised form 30 September 1998; accepted 12 November 1998 Abstract This work was performed to evaluate the eect of electrical stimulation (ES) on pH fall and meat quality of LD and BF in Danish halothane free pigs stunned with CO 2 . ES resulted in a signi®cant drop in pH of 0.3 units in both LD and BF and 3 h lairage resulted in 0.1 units lower pH at 20 min post mortem. Lairage time did not aect and did not interact with the eect of ES on any of the measured meat quality parameters. ES did not aect the ultimate pH in LD, BF, SM and SC or internal re¯ection value in LD. However, ES caused higher internal re¯ection and drip loss in BF and increased the PSE frequency in LD (2 to 7%) and in BF (2 to 49%). The frequency of PSE areas in the centre of SM was 70% for ES pigs compared to 9% for control pigs. ES and ageing improved the tenderness and reduced the hardness in LD as well as shear force of unaged BF. The eect of ES on tenderness and hardness was approximately half the eect of ageing, but the eect of ES and ageing were additive. ES signi®cantly increased the activities of cathepsin B+L in the myo®brillar fraction, but there were no dierences in proteolytic activity in the other frac- tions. It is concluded that ES improves tenderness in LD and BF, but has a negative eect on the quality of BF and SM. Therefore ES is not an economically attractive alternative for improvement of tenderness in LD compared to ageing in Danish pigs. # 1999 Elsevier Science Ltd. All rights reserved. Keywords: Pigs; Electrical stimulation; pH; Drip loss; Sensoric quality; Cathepsin B+L 1. Introduction Cold induced muscle contraction is a potential meat quality problem as it induces toughening in pork when rapidly chilled. Various treatments have been reported to avoid cold toughening. It has been shown, that high voltage electrical stimulation (ES) 20 min post mortem in combination with fast chilling improves tenderness in pig M. Longissimus Dorsi (LD) without increasing drip loss (Taylor & Tantikov, 1992; Taylor, Nute, & Warkup, 1995b; Taylor & Martoccia, 1995). Low vol- tage ES performed immediately after exsanguination gave variable results with respect to tenderness but in general resulted in increased drip loss and paler colour (Gigiel & James, 1984; Mùller, Kirkegaard, & Vester- gaard, 1989; Taylor & Tantikov, 1992) and is therefore not recommended. Other ways of improving tenderness are ageing (Bejerholm, 1991), and hip suspension (Mùl- ler, Kirkegaard, & Vestergaard, 1987; Drans®eld, Led- with, & Taylor, 1991) which can be considered as alternatives to ES (Taylor, Perry, & Warkup, 1995a). ES leads to muscle contractions and accelerates mus- cle metabolism and pH fall pre rigor. Depletion of the energy in the muscle decreases time to rigor and pre- vents contractions during the initial chilling period or at rigor (Cross, 1979; Marsh, 1986). A fast pH fall is known to induce protein denaturation (Oer, 1991), but these eects are reduced when ES is used in combina- tion with fast chilling (Honikel & Regan, 1986; Taylor & Tantikov, 1992; Taylor et al., 1995b). ES used in combination with slow chilling causes a high degree of protein denaturation, but has shown variable results with respect to tenderness (Drans®eld et al., 1991; Tay- lor & Tantikov, 1992; Warriss et al., 1995). The mechanisms for improvement of tenderness in ES carcasses have been intensively discussed. Prevention of cold shortening, mechanical disruption of myo®brils Meat Science 52 (1999) 179±187 0309-1740/99/$Ðsee front matter # 1999 Elsevier Science Ltd. All rights reserved. PII: S0309-1740(98)00166-1 * Corresponding author. Tel.: +45-3373-2626; Fax: +45-3314- 2517; E-mail: hma@ds-data.dk